Preservation of rubber



Patented June 2, 1942 PBJ'ISERIA'I'ION OF RUBBER Frederick B. Downing,Carneys Point, N. 1., Ar-

thur M. Neal, Wilmingt on, Del., and Charles J.

Pedersen, Penna Grove, N. 1., assignors to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware No Drawing.Original application December 29,

1937, Serial No. 182,374.

Divided and this application January 20, 1938, Serial No. 185,928 1':Claims. (c1. zso -sos) This'invention relates to the preservation ofrubber, particularly inthe presence of copper and its compounds whichcatalyze the deterioration of rubber due to the action of heat andoxidation.

It is well lcnown that certain substances, for

example the secondary aromatic amines, possess the power of retardingthat deterioration of rubher which is due to heat and oxidation. It isalso to oxidation. Thus as small an amount of copper moles of anortho-hydroxy substituted aldehyde which is aromatic in nature, so thatnot more mary amino group of the amine.

than one mole of aldehyde reacts for each pri- The polyamine may be anyaliphatic amine containing at least. two primary amino groups directlyattached to different carbon atoms of the same open chain and whichamine. may, constearate as .00l% based on the rubber will increase therate of deterioration due to. heat and oxidation several hundredpercent. This great catalytic activity of copper necessitates expensiveand tedious processes to insure that all copper isremoved fromcompounding agents. It is also necessary to be sure that no copper isintroduced through contamination during the processing of the rubber. Ithas been proposed heretoiore to overcome this catalytic action throughthe use of well known antioxidants such as phenylb-naphthylamine. Suchcompounds, however, are relatively ineffective in overcoming thecatalytic action of the copper.

An object of the present invention is to provide a new class ofcompounds which are effective in overcoming the catalyticaction ofcopper on I that deterioration which rubber normally undergoes due tothe action of heat and oxidation. A

the rings.

tain aromatic or other cyclic groups substituted on the chain. Thetermaliphatic.polyamine" as employed hereinafterv and in the claims willbe. understood to have the foregoing meaning. The polyamine may bean'aromatic or other cyclic amine having at least two primary aminogroups attached to ditlerent substantially adjacent atoms of the ring orrings, either directly or through one or more atoms which are notmembers of consisting of carbon, hydrogen and nitrogen, those in whichat least two primary amino groups are directly attached to adjacentcarbon atoms,

. and particularly the diamines.

further object is to retard the deterioration of rubber due to heat andoxidation even in the presence of copper and its compounds whichnormally accelerate such deterioration. A still further object is torender the usual rubber anti-j oxidants effective even in the presenceof copper and its compounds inthe presence of which such antioxidantsare usually relatively ineffective. Other objects are to provide newcompositions of matter and 'tcadvance the art. Still other objects willappear hereinafter.

These objects may be accomplished in accordance with our invention whichcomprises incorporating in the rubber'a small amount of an organiccompound containing .an ortho-hydroxy' By substantially adjacent atoms,we mean only ring atoms directly bonded together and ring atoms locatedin different nuclei of polynuclear compounds which ring atcmsare the twoatoms, not common to two rings nor forming part of the linkage betweentwo rings, nearest to each other. By adjacent atoms, we )mean atomsdirectly bonded together. Bypolynuclear compounds, we mean to includecompounds containing two or more rings having no ring carbonatoms incommon as well as fused ring compounds.

By an ortho-hydroxy substituted aldehyde",

we mean one in which the hydroxy group and the aldehyde, or CHO, grouparedirectly bonded to adjacent ring carbon atoms. By the term aldehyde,aromatic in nature, we intend to include the unsaturated cyclicaldehydes, such as thepyridine and guinoline aldehydes, which have manyof the characteristic properties of the aromatic aldehydes, as well asthe strictly aromatlc 'aldehydes in which the hydroxy and aldearomaticgroup and a tertiary nitrogen having hyde groups are bonded to nuclearcarbon atoms of an aromatic ring.

The aldehyde is preferably an aromatic-aldehyde and also preferably onedevoid of substituand a small amount of a rubber antioxidant of adifferent type. The organic compound above referred to is a type ofarylidene amine or Schifis base, obtained by condensing one mole of apolyamine, containing. at least .two primary amino cuts other thanhydrocarbon and hydroxy groups. However, such aldehyde may contain, assubstitutents,alkoxy, aryloxy, halogen, heterocyclic, amino, cyano,carboxyl and sulfonic groups as well as hydroxy, alkyl and arylradicals. The polyamine may be likewise. substituted, but is preferablyunsubstituted.

The preferred polyamines are those 1 .ing stocks were prepared.

Compounds of this type are well known and methods of making them aredescribed by Mason,

. Ber. 20 267-277 (1887') and Haegele Ber. 25 2753-2756 (1892). They arefurther discussed aseiaaeo erful antioxidant as shown by test A, it isrelatively inefiective when the oxidation is catalyzed by the presenceof copper salts, tests B and C. It will be seen, however, thatdi-salicylal ethylby N. -U. Sidgwick in his books The Electronic 5 shediamlne overcomes the catalytic actionot Theory of valency," Oxford 1027and "The copper almost completely. Thus stocks D and Covalent Link inChemistryflCor-nell 1933. E, which contain this compound in addition toThe above compounds are, in general, relathe copper, are substantiallyas good after aging tlvely ineiifective in retarding that deteriorationas stock A which contains no copper. I

which rubber undergoes due to heat and oxide.- In order to still furthertest these compounds, tion, in the absence of metal catalysts, and-hencethe following stocks were prepared;

they are not valuable commercially as antioxidents. However, we havefound that. when such A B 0 compounds are employed in. rubber and in thepresence of an antioxidant of a difierent type, 100 m 100 they tend toinhibit or neutralize the catalytic g g eflect of copper and itscompounds, and hence Lithopone a1) a l are hereinafter named copper.deactivators, for

convenience. In inhibiting the deterioration of git y i 'bggtgifi iiii13 rubber due to heat and oxidation the usual antis oxidants aresubstantially ineflective in the D5 icylamphenylene diamme .presence ofcopper and its compounds when such antioxidants areemployed alone. Our.com-

pounds, when-employed alone, have little if any, preservative eii'ectonrubber whetherv in the presence or absence of copper and its com!.pounds. i

The *quantity of copper deactivator, added will per 01'' its compound isaccidentally present.

Higher ratios of copperdeactivator may be used, particularly when therubber is in contact with Completely deteriorated.

metallic-copper in bulk which forms-,areservoir of-co'p'per ions. i r

.Inorderjo test these compounds, the follow- These stocks were cured forminutes at 40 lbs. steam pressure. They were tested by charging samplesin a Bierer Davis bomb at 70 C. and

300 lbs. oxygen pressure ior 5 days and then determining their physicalproperties. The results of this test are given in the following bedependentupon the amount of copper present 1? Table IA ln-ithe-rubber.At least one mole of, copper de- 30 1 I V activatormust be added foreachatomof cop- I per'ln'the rubber. iPreterably, from about 1.5 stockTensile g g; to about ;100 moles of copper deactivator is used 18ml days.ior eachatom of copper in the rubber. From about 0.0002 to about 1.0%of copper deactivator 35 616 ,825

- based on-- the rubber will generallybe 'satisfac 31;; g 600tory-in'most rubber compositions where the cop- These tests show thatdisalicylal-o-phenylene diamine is also a very eilective compound inovercoming the catalytic efl'ect of copper. Thus, whilephenyl-bmaphthyiamine is relatively ineffective in the presence ofcopper, the disalicylal- 'o -phenylene diamine inhibits the action ofcopper and renders the phenyl-b-naphthylamine ei- B D E rective.

In order to show that this remarkable increase 1% igg 18g ineffectiveness was due to overcoming the catauli a s 3 a a lytic activityof the copper and not merely an I Who In 5 additive effect due to theincreased concentration me otolylguanidina. 0.15 0.75 0.15 0.15 0.15 ofantioxidant, the following stocks were pre- Phenyl-b-napbthylamine 1.001.00 1.00 1.00 1.00 .Copperltestate uue-.. 1 .05 0.1 .06 0.1

,Di-sali ylal'etbyle F'I-These stocks were cured for 45 minutes at 40--l .;steam'pressure.'- Theywere tested by hangi'rigfsamples in'ajBierer'Davis bomb at C. and =300- lbs. oxygen pressure ior 5'days andthen- "determining'their'physical properties. The reultsot-this test"are given in Table I.

. ifljr'aezer These stocks were cured for 46 minutes at 40 Tame lbs.steam pressure. They were tested by the e p u 65 same "oxygen born-b"test described above. The 5 am results of this test are given in TableII.

. 3,8,6 m5 Table I1 2.3 (l) m 80o m Tensile c mpile,-deterioratedlntwodays. v L a 50 1' It will be seen from this table that,whereas MW 2.326

phenyl-b -naphthylamine is an' extremely powhexamethylene tetramineThese tests show that there is little or no improvernent in the normalaging of stocks containing phenyl-b-naphthylamine when these copperinhibitors are added in the'absence oi copper or its compounds which actas catalyzers of oxidation.

In order to further show that the results ob tained are due to thecombined action of the compounds and not due to'either one alone, testswere made with the following stocks:

A .B C D 100 100 100 100 ii!) 100 3 3 3 1 1 l l 21 I) a) Di or ho tolylguanidino 0. 75 0.15 0. 75 0. 75 Copper atearate 0.05 0.1 0.06 0.1 Phenlb-naphthylamine 1.0 1.0 Di icylal ethylene diaminc. 1.0 1.0

These stocks were cured for 45 minutes at 40 lbs. steam pressure. Theywere tested by hanging samples in a Bierer-Davis bomb at 70 C. and

p 300 lbs. oxygen pressure for 3 days and then determinin'g theirphysical properties. Theresults of this test are given in Table III.

Table III Tensile Tc'nsfleaitcrada in. original bolnb ajm Comdeteriorated. 3.21 it? 3,215 Do. 3,515 Do.

1 Titone is a titanium l'eeniorccd lithopone containing about 15%titanium dioxide, 60% barium sulfate, and 25% ring sulfide. (SecCompounding ingredients for Rubber," copyright 1030, Bill BrothersPublishing Company, p. 147). r

I Heliozone is the trade name of a specially selected group of waxmaterials. (See "Compounding Ingredients for Rubber," B BrothersPublishing Company, 1936, p. 72). e

1 Acrin is the trade name oi an accelerator made by condensing benzylchloride, and tmcrnplohenmthiazole according to the d sclosure of UnitedStates Patent 1378,654-

l Antox is the trade name of the butyruldchyde-amlinc condensationproduct made according to United States Patent 1,029,102.

These stocks were cured in lbs. air pressure with acne hour rise to 250'1'. followed by a half hour at 250 F. The will! properties bomb by theusual Bierer Davis test. The re-' suitsot this test are given in TableIV.

Table IV Tensile. Stock w m1 A- 475 150 B. too 0 gm 1, m

p etely deteriorated.

It can be seen. from this table out, in this test also, where abutyraldehywm condensation product was used in place ofphenyl-bnaphthylamine, the compounds disclosed are efiective inovercoming the catalytic activity of copper.

Although tests have been disclosed'in which these compounds areusedwitheither phenyl b-naphthyiamine or butyraldehyde-aniiine as antioiddants,they m y be used with an! o! the known antioxidants for rubber. kamplesoi' other compounds, which may be used as antioxidants alone with theinhibitors for copper,

are phenyl-a-naphthylamine, aceione-diphenylamine condensation product,acetone-aniline condensation products and their 'polymerizaflonproducts, diphenyl-ethylene-diamine, acetaldehyde-aniline,aldol-a-naphthylamine, p(OH) phenyl morphoiine, dicatechol borate,diphenyiamine, diphenyl-p-phenylene diamine, di-bnaphthyl-p-phenylenediamine, 4(p-toluene sui- Ionyl amino) 4' methyl diphenylamine, etc.

Examples of other compounds, which act as inhibitors or the catalyticoxidation due to the presence of copper, are the following:

' Other eiiective copper deactivators ior inhibiting the action ofcopper and its compounds on the oxidation of rubber may be made bycondensing each o! the following aldehydes with each of the followingpolyamines:

4M1: v .Polnmim 2 0 bans-aldehyde Methylene diamiuo 0 B-chlmobenuldehydeEthylene diaminc 0 3,5-dibromcbcnzaldahydo 1,2-propylenc diamino 2(011S-nitro Ydo ,ii-propylcnc diamine 3 0H G-mcthyi henzaldch doLiO-dccylonc 0H z-mctlioxy benuldehydc Dicthyleno triaminoiiiii8tfihhiii: %"""fihi' n c 2 ontaeryt ty tctramino 2 0H;a-cyanobcnzal chyde 1,2-diamino cycl hcnno 2 0H secarboxybenraldcliydcLzdiamino banana OI? bcncaldohydo-a suli'onic 2,34iaminc pyridine acl2,3-diamino naphthridina-Ll IiOH) naphthaldehyde'l 4,5-diamino quinollna1 0H) naphtbaldchyde-2 1,8-diaminonaphthalcne An -2aldehydo-l 1, aminoanthraquinono 2 OH) fluorenealdohyde-l 3,4-dlamino dl bony] 4 0H)diphcnyl aldehyde-3 9,l0-diamino pYienanthrcno 3 ?H)8honantliranoaldehyde-4 3,4-toluylcno diamlnc 1, di( H)-2,4-dicldoliydrobonziailamino diphonyl:

lone iamlno phcnant relic 4(0H) pyridino-aldchyda-fl 4(OH)qulnolino-aldehyde-S 7(0H quinolinc-aldahyde-B In en or the testsdisclosed, the compounds were added according to the usual methods oi oithese stocks were determined in the oxygen incorporatins'beiorevulcanization. It shouldbe 4 Q pointed out, however, thatthey'can beused as eilectively by incorporating them into the rubber stock aftervulcanization by any of the well known processes or difiusion. Thesecompounds can alsobe used effectively by introducing them into latex,either natural or synthetic.

When-we reier to the catalytic eflect oi copper herein and inthe claims,it will be unders that we refer to copper in the form of its salts orother catalytically active compounds as well as in the form or the puremetal.

While we have disclosed the preferred embodiments of our invention, itwill be readily apparent in those skilled in art that many variationsand modifications may be made therein without departing from the spiritof our invention. Ac-

cordingly, the scope 0! our invention is to be limited solely by theappended claims, construed as" broadly as is permissible in view of theprior art.

. This is a division of our copending applies-=- tlon Serial No.182,374, iiled December 29, 1937.

.We claim: v

1.-The method of retarding the deterioration of vulcanized rubber, dueto the catalytic eflect of copper in contact with the rubber, in thepres ence of an antioxidant which is normally efiective to materiallyretard the deterioration of the copper deactivate: identical with thecompound,

obtained by condensing 1 mole of a primary cyclic polyamine solely withat least 2 moles 01 an ortho hydroxy substituted aldehyde, aromatic innature, so that not more than 1 mole oi aldehyde reacts for each primaryamino group of the polyamine, said.polyamine containing at least twoprimary amino groups attached to different substantially adjacent ringatoms.

2. The method of retarding the deterioration of vulcanized rubber, dueto the catalytic efl'ect 01' copper in contact with the rubber, inthepresence of an antioxidant which is normally effective to materiallyretard the deterioration of the cient to inhibit the catalytic effect ofcopper, a copper deactivator. identical with the compound obtained bycondensing 1 mole of a primary aromatic polyamine solely with at least 2moles of an ortho hydroxy substituted aromatic aldehyde, so that notmore than 1 mole of aldehyde reacts for each primary amino group of thepolyamine, said polyamine consisting of carbon, hydrogen and nitrogenand containing at least two primary amino groups directly attached todifiere'nt substantially adjacent carbon atoms.

4. The method of retarding the deterioration of .vulcanized rubber, dueto the catalytic eiiect of copper in contact with the rubber, in thepresence of an antioxidant which is normally effective to materiallyretard the deterioration oi the vulcanized rubber due to light, heat andoxidation in the absence of copper but which is less effective in thepresence oi copper, which comprises incorporating in the rubber in theproportion of from about 0.5% to about 1.0%, suihcient to inhibit thecatalyticeiiect of copper, a disalicylal-ophenylene diamine.

A 5. The method of retarding the deterioration oi' vulcanized rubber,due to the catalytic effect of copper in contact with the rubber, in thepres ence of an antioxidant which-is normally effective to materiallyretard the deterioration of the vulcanized rubber due to light, heat andoxidation in the absence of copper but which is less effective in thepresence oi copper, which comprises incorporating in the rubber in theproportion 01 from about 0.5% to about 1.0%, sufilcient to inhibit thecatalytic effect of copper, disalicylal-ophenylene diamine.

6. The method of retarding the deterioration of vulcanized rubber, dueto the catalytic effect 01 copper in contact with the rubber, in thepresence of 'a phenyl-naphthylamlne, which comprises incorporating inthe rubber in the proportion or from about 0.5% to about 1.0%,suflicient to inhibit the catalytic efiect of copper, a

vulcanized rubber due to light, heat and oxidation lwdroxy substitutedaromatic aldehyde, so that not more than 1 mole of "aldehyde reacts toreach primary amino group 0! the polyamine, said polyamine consisting ofcarbon, hydrogen and nitrogen and containing at least two primaryamino'groups attached to different substantially adjacent ring atoms,and said aldehyde consisting of theele'm'ents carbon, hydrogen andoxygen. 3. The method or retarding the deterioration ofvulcanizedrubber, due to the catalytic efiect of copper'in contact withthe rubber, in the .presence of an antioxidant which is normallyeffective to materially retard the deterioration oi the vulcanizedrubber due to light, heat and 0111- I dation inthe absence of copper butwhich is less effective in the presence or copper, which comprisesincorporating in the rubber in the proportion of from about 0.5% toabout 1.0%, sufll- 9. Vulcanized rubber disalicylal-o-phenylene diamine.

7.'The method of'retardlng the deterioration oi vulcanized rubber, dueto the catalytic eilect of copper in contact with the rubber, in the fpresence of phenyl-b-naphthylamine, which comprises incorporating in therubber in the proportion from about 0.5% to, about 1.0%, sumcient toinhibit the catalytic effect of copper, disalicylal-o-phe nylenediamine.

8. Vulcanized rubber having incorporated therein a small amount of anantioxidant which is normally effective to materially retard thedeterioration of the vulcanized rubber due to light,

heat and oxidation in the absence oi. copper but which is less eflectivein the presence of copper, and from about 0.5% to about 1.0%, sufflcientto inhibit the catalytic effect of copper, of a copper deactivatoridentical with the compound obtained by condensing 1 mole of a primarycyclic polyamine solely with at least 2 moles of an ortho hydroxysubstituted aldehyde, aromatic in nature, so that not more than 1 moleof alde- 'hyde reacts for each primary amino group of the polyamine,said polyamine containing at least two primary amino groups attached todifferent substantially adjacent ring atoms.

having incorporated therein a small amount of an antioxidant which isnormally eiiective to materially retard the deterioration of thevulcanized rubber due to light, heat and oxidation in the absence ofcopper but which is' less effective in the presence of copper, and fromabout 0.5% to about 1.0%,

, 2,285,260 'sufllcient to inhibit the catalytic effect of copper,

of a copper deactivator identical with the compound obtained bycondensing 1 mole of a primary cyclic polyamine solely with at least 2moles of an ortho hydroxy substituted aromatic aldehyde, so that notmore than 1 moleof aldeper but which is less effective in the presencehyde reacts for each primary amino group of, the polyamine, saidpolyamine consisting of of copper, and fromabout 0.5% to about 1.0%,

sufficient to inhibit the catalytic efiect of copper, of a copperdeactivator identical with the compound obtained, by condensing 1 moleof a primary cyclic polyamine solely with at least 2 moles of an orthohydroxy substituted aromatic aldehyde, so that not more than 1 mole ofaldehyde reacts for each primary amino group --ot the polyamine, saidpolyamine consisting of carbon, hydrogen and nitrogen and containing atleast two primary amino groups attached to different substantiallyadjacent ring atoms, and said aldehyde consisting of the elementscarbon, hydrogen and oxygen.

11. Vulcanized rubber having incorporated therein a small amount of anantioxidant which hydrogen and nitrogen and containing at least twoprimary amino groups directly attached to different substantiallyadjacent carbon atoms.

12. Vulcanized rubber having. incorporated therein a small amount of anantioxidant which is normally effective to materially retard. thedeterioration of the vulcanized rubber due to light, heat and oxidationin the absence of copper but which is less efiective in the presence ofcopper, and from about 0.5% to about 1.0%,

sufficient to inhibit the catalytic efiect of coppe of adisalicylal-o-phenylene diamine.

13. Vulcanized rubber having incorporated therein a small amount of anantioxidant which normally effective tomaterially retard thedeterioration of the vulcanized rubber due to light, heat and oxidationin the absence of copper but which is less effective in the presence ofcopper, and from about 0.5% to about 1.0%, sufficient to inhibit thecatalytic effect of copper,

of disalicylal-o-phenylene diamine.

is normally effective to materially retard the amine, said polyamineconsisting of carbon,

14. Vulcanized rubber having therein a small amount of aphenyl-naphthylamine, and from about 0.5% to about 1.0%, sufficient toinhibit the catalytic effect of copper, of a disalicylal-o-phenylenediamine.

15. Vulcanized rubber having incorporated therein a small amount ofphenyl-b-naphthylamine, and from about 0.5% to about 1.0%, sufiicienttoinhibit the catalytic effect of copper, of disalicylal-o-phenylenediamine.

16. Vulcanized rubber having incorporated therein a small amount ofbutyraldehyde-aniline condensation product as an antioxidant, and fromabout 0.5% to about.1.0%, sufiicient to inhibit the catalyticeffect ofcopper, of disalicylal-o-phenylene diamine.

17. Vulcanized rubber having incorporated therein a small amount ofacetone-diphenylamine condensation product as an antioxidant, and fromabout 0.5% to about 1.0%, suffi'cient to inhibit the catalytic effect ofcopper, of disalicylal-o-phenylene diamine.

' FREDERICK B. DOWNING.

ARTHUR M. NEAL. CHARLES J. PEDERSEN.

incorporated

